Some Republicans are siding with Democrats around the proposition that online sales should be taxed. Now, Congress is adding a rider to the National Defense Authorization Act that would allow such a tax. The so-called Marketplace Fairness Act, which also has a House counterpart, the Marketplace Equity Act, will allow states to collect sales taxes on retailers who are located out of state.

obamadash (Photo credit: GunnyG1345)

This would be a fundamental expansion of states’ power to tax; it arguably violates the privileges and immunities clause, allowing states to set up tariffs against other states’ businesses…